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Algebraic and geometric theory of quadratic forms and symmetric bilinear forms, e.g., values attained by quadratic forms, isotropic subspaces, the Witt ring, invariants of quadratic forms, the discriminant and Clifford algebra of a quadratic form, Pfister forms, automorphisms of quadratic forms.

4 votes

Can a positive binary quadratic form represent 14 consecutive numbers?

Here's a heuristic that suggests why arbitrarily large strings of consecutive numbers should be representable by some binary quadratic form. For simplicity consider a prime $p$ that is $3\pmod 4$ s …
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7 votes
Accepted

Achieving consecutive integers as norms from a quadratic field

The answer to Speyer's question as stated is no, this need not be the case. To see this let $p\equiv 3\pmod 4$ be a prime and consider the associated imaginary quadratic field ${\Bbb Q}(\sqrt{-p})$ …
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8 votes

Counting fundamental units of real quadratic fields

In Proposition 4.1 of Sarnak you'll find an asymptotic for the related quantity (take there $p=1$) when one considers all ring discriminants (not just the fundamental field discriminants that you want …
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6 votes

Questions on $x^2+y^2+z^2$, $x^2+y^2+2z^2$ and $x^2+2y^2+3z^2$

Problems like Question 1 go back to Euler and Gauss. This question is essentially asking which idoneal numbers are sums of two squares. There is a famous open problem going back to Euler and Gauss a …
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19 votes
Accepted

Upper bound on answer for Pell equation

Let $d$ be a positive fundamental discriminant, $\epsilon_d$ denote the fundamental unit, $h(d)$ the class number, and $\chi_d$ the primitive character associated to the discriminant $d$. The class n …
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19 votes
Accepted

Many representations as a sum of three squares

The formula for $r_3(n)$ essentially connects this with a class number of an imaginary quadratic field, or (apart from the $\sqrt{n}$ scaling) with the value of an $L$-function at $1$. So your questi …
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